Mechanically and electrically split keyboards are known in which multiple keyboards or keyboard components communicate with a common host (e.g., computer terminal). Such split keyboards can be desirable, for example, to improve user comfort (as disclosed in U.S. Pat. No. 5,424,728) or to allow a keyboard to be greatly reduced in size (e.g., for storage in a compact area) without compromising key button size. The split keyboards typically are each provided with a separate communication means to communicate with the host electronic device. The split keyboards can communicate with the host either by a wire connection or by wireless technologies such as infra-red technology, radio frequency (RF) signals, magnetic signals, etc. A significant problem in such systems relates to insuring that the split keyboards can reliably communicate with the host electronic device. Reliable communication can be made difficult due to interference resulting from the split keyboards attempting simultaneous communication with the host electronic device, or resulting from external interference sources.
Known methods and systems for synchronizing communication between multiple devices and a common host electronic device include hard-wire connections between the multiple devices and the common host electronic device. Known wireless communication methods and systems between multiple devices and a common host include systems such as electronic or video games. A keyboard has significantly more performance requirements than an electronic game keypad; it is far more difficult to synchronize wireless communication between split keyboard devices and a common electronic host. Accordingly, these known methods of synchronization are undesirable for keyboard applications.
U.S. Pat. No. 5,189,543 to Lin et al. discloses an infra-red wireless keyboard system which allows multiple users to operate wireless keyboards without interference. According to this system, each channel is programmed with an individual identifier code and an individual carrier frequency. When a key is depressed, the key code and ID code are transmitted according to the known RS-232 format at a designated frequency. The carrier frequency is designated by the user, and is selected from a range of frequencies. Because the ID codes and carrier frequency associated with each channel is different, multiple users can transmit simultaneously and the common receiver can be tuned to accept only a desired carrier frequency. As should be readily apparent from this description, the system of the Lin patent is undesirably complicated.
It would be desirable for a split keyboard communication system and method to incorporate a relatively simple communication protocol for ensuring reliable communication between two or more split keyboards and a common electronic host.